drm/i915/pmu: Work around compiler warnings on some kernel configs

Arnd Bergman reports:
"""
The conditional spinlock confuses gcc into thinking the 'flags' value
might contain uninitialized data:

drivers/gpu/drm/i915/i915_pmu.c: In function '__i915_pmu_event_read':
arch/x86/include/asm/paravirt_types.h:573:3: error: 'flags' may be used uninitialized in this function [-Werror=maybe-uninitialized]

The code is correct, but it's easy to see how the compiler gets confused
here. This avoids the problem by pulling the lock outside of the function
into its only caller.
"""

On deeper look it seems this is caused by paravirt spinlocks
implementation when CONFIG_PARAVIRT_DEBUG is set, which by being
complicated, manages to convince gcc locked parameter can be changed
externally (impossible).

Work around it by removing the conditional locking parameters altogether.
(It was never the most elegant code anyway.)

Slight penalty we now pay is an additional irqsave spin lock/unlock cycle
on the event enable path. But since enable is not a fast path, that is
preferrable to the alternative solution which was doing MMIO under irqsave
spinlock.

Signed-off-by: Tvrtko Ursulin <[email protected]>
Reported-by: Arnd Bergmann <[email protected]>
Fixes: 1fe699e30113 ("drm/i915/pmu: Fix sleep under atomic in RC6 readout")
Cc: Tvrtko Ursulin <[email protected]>
Cc: Chris Wilson <[email protected]>
Cc: Imre Deak <[email protected]>
Cc: Jani Nikula <[email protected]>
Cc: Joonas Lahtinen <[email protected]>
Cc: Rodrigo Vivi <[email protected]>
Cc: David Airlie <[email protected]>
Cc: [email protected]
Cc: [email protected]
Reviewed-by: Chris Wilson <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]
(cherry picked from commit ad055fb8e010e4ff37f66aeed1d380329bddce67)
Signed-off-by: Joonas Lahtinen <[email protected]>

0 files changed, 0 insertions, 0 deletions